MySQL中复合主键的外键关系

Question

Which is the best way to create a relationship between two tables when referenced table has a composite primary key?

table1{
   id,
   name
}

table2{
   id1,
   id2,
   name
}PrimaryKey(id1, id2)

Answer 1

The only way is using both keys:

alter table t add constraint fk_t_id1_id2
    foreign key (id1, id2) references table2(id1, id2);

However, I would encourage you to add an auto-incrementing column to table2 so such relationships can use a single key.

Answer 2

One way is this

alter table t add constraint fk_t_id1_id2
foreign key (id1, id2) references table2(id1, id2);

As Gordon said, the best option is create an auto incremental ID and make this the primary key.